This invention relates to a child resistant safety closure for a neck of a container. More particularly, this invention relates to a child resistant safety closure for a container that has a common single start thread, the closure having a structure that is easily deformed for clearance over a locking projection.
There is a constant need for child resistant closures that can easily be opened by adults, and in particular, closures that can be opened easily by elderly adults, but yet cannot be easily opened by young children. In this regard, there must not be a requirement of a vigorous twisting motion or of a strong squeezing in combination with a twisting. The reason is that many people through injury or disease, such as arthritis, have difficulty in gripping and/or twisting a closure to remove the closure from the container. On the other hand, the closure must not be easily removable by a small child. These are two competing requirements that must be considered in the design of a child resistant safety closure.
This problem has been addressed in various ways in the prior art. In U.S. Pat. No. 3,376,991 there is shown a bottle where the container has more of a rectangular shaped dispensing neck. This permits the closure to be flexed inwardly at these points so that the closure at a point about 90.degree. from the point where pressure is applied will bow outwardly. This then permits closure projections on the inner surface of the closure and spout projections on an outer surface of the spout to clear each other and the closure can be removed from the spout in a twisting action. A related structure is disclosed in U.S. Pat. No. 3,841,514. In this closure, there is an inner skirt on the closure for threaded attachment to a container neck and a flexible outer skirt that has a locking arrangement. The outer skirt also has slots that allow for a greater flexing of the outer wall during squeezing and opening. By squeezing the outer flexible skirt the outer skirt is distorted in shape so that locking projections are released and the closure can be removed. U.S. Pat. No. 3,984,021 discloses a closure for a bottle where the bottle neck has two flattened areas. Locking projections are located about 90.degree. from these flattened areas. There are two locking projections and two flattened areas. When the closure is pressed in the area of the flattened areas of the neck, the closure in the area of the projections protrudes outwardly to release the locking mechanism.
These are interesting closures but they have disadvantages. There is yet a very high squeeze pressure needed to release the closure. That is, it takes too much force to deflect the walls of the closure to release the locking mechanism. Further, there is no need for a dual locking mechanism. That is, there is not a need for two projection locking means 180.degree. apart. A single locking means would suffice. The use of a single locking means allows for the use of single start threads, which are also known as common threads since they are used on most containers. The use of single start threads increases the utility of the closure and container. The same container can be used for child resistant safety use and regular use by using a container with a child resistant feature and a closure with or without a child resistant feature as needed. In the alternative the same closure can be used for standard containers not using a child resistant safety closure and containers which use a child resistant safety closure. For a child resistant safety closure requirement there would be a child resistant feature such as a projection on the outer surface of the container neck to interact with a mating projection on the inner surface of the closure. When a safety closure is not required there would not be the projection on the neck of the container or on the closure. One of these projections would be deleted. In a preferred embodiment it is preferred that the projection on the closure be deleted. The same container then would be used in all instances with one closure when child resistance is desired and another closure when it is not desired. In this latter instance, the closure can be freely removed from the container.